1. Field of the Invention
The present invention relates generally to a cooling system monitor and, more particularly, to the use of differential pressure to determine whether a sufficient flow of cooling water is passing through the cooling system of an internal combustion engine.
2. Description of the Prior Art
U.S. Pat. No. 3,739,366, which issued to Lace on Jun. 12, 1973, describes a flowmeter for an engine cooling system. The flowmeter senses the flow rate in an engine cooling system to provide an indication of an extraordinary condition as when the water pump or one of the fluid conducing hoses becomes inoperative. The flowmeter sensor comprises a pair of stationary electrodes located adjacent to and on either side of a flexible electrode which is deflected by the current flow. A relatively high frequency alternating current produces a field between the two stationary electrodes and the deflecting electrode will assume a potential base on its location in the field. A threshold detection circuit is connected to the deflecting electrode whereby a change in its apparent voltage will actuate a warning device.
U.S. Pat. No. 4,682,493, which issued to Tenenbaum on Jul. 28, 1987, describes a cooling system monitor. Apparatus for monitoring the cooling system of a liquid cooled automotive engine is described. The apparatus provides a warning of a malfunction within the system and diagnostic information of what the malfunction is. The compact apparatus is easily mounted on the inlet radiator hose and includes elements for measuring the coolant level, flow rate, pressure and temperature.
U.S. Pat. No. 3,793,997, which issued to Banner on Feb. 26, 1974, describes an engine liquid flow indicating device means. Liquid flow sensors connected to an engine or power means requiring liquid cooling are described. Sensors measure liquid flow velocity and volume factors on a visual flow gauge in increments of low, medium and high volume readouts in conjunction with a warning means, for liquid flow and pressure indication.
U.S. Pat. No. 4,062,231, which issued to Mercik et al on Dec. 13, 1977, describes engine cooling system diagnostics. A single pressure transducer tapped into the cooling system of an engine, downstream of the pump, is used to measure coolant pressure at high idle and coolant pressure at low idle while the water temperature is such as to assure the thermostat is closed. The pressure readings are equivalent to the pressure across an orifice or restriction formed by the coolant bypass when the thermostat is closed. The combination of high idle pressure and difference between high idle pressure and low idle pressure permit diagnosing whether the pump is faulty or whether there is unduly large restriction in the engine, which otherwise could not be known with a single pressure reading.
U.S. Pat. No. 5,996,331, which issued to Palmer on Dec. 7, 1999, describes a passive turbine coolant regulator responsive to engine load. A passive feedback-controlled regulator and method for regulating gas turbine bleed air is provided, which automatically regulates the flow of coolant air directed to the turbine vanes, blades, and other hot section components based on the inherent differential pressure between the diffused compressor discharge pressure and the compressor impeller exit air. The differential pressure used to operate the regulator is a measure of the turbine mass flow rate, and, therefore is a measure of the instantaneous engine coolant flow requirement.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.